The A38 Exeter-bound has been partially reopened while work to recover an overturned fuel tanker continues.
But drivers are still experiencing delays, with traffic queueing near the scene of the accident.
The northbound carriageway was completely closed for several hours on Saturday morning following a collision between the lorry and a car near Buckfastleigh.
Both drivers were taken to hospital but are not believed to have suffered serious injuries.
Police say the lorry has slipped down a bank and is in a difficult situation for recovery due to still being fully laden with fuel.
A Devon and Cornwall Police spokesman said: "A fully laden fuel truck has slipped down a bank and is in a difficult position to get recovered from. Fire and Highways will lead the operation but they will probably have to empty the tanker before it can be recovered.
"The accident involved a car and the truck and two drivers were taken to A&E as a precaution. We do not believe there are any serious injuries."
Fire officers said the vehicle was a 'long way' down the bank and quite far from the carriageway so a crane may be needed to help in the recovery operation.
The crash happened on the northbound carriageway between Buckfastleigh and Ashburton shortly after 7am on Saturday.
A local diversion was set up from Dartbridge to Peartree via the B3352. Updates as we have them.
